After ejaculation, mammalian sperm is activated for motility acquisition and capacitation. The activation process is a reaction, which takes place before the acrosome reaction or before sperm encounters egg and is a reversible reaction depending upon a decapacitation factor (DF) contained in the seminal fluid.
Motility acquisition of sperm is a phenomenon required for enabling the acrosome reaction of sperm. Furthermore, motility acquisition and capacitation simultaneously occur and these two sperm activation phenomena both are essential for fertilization. Capacitation is defined as a series of biochemical reactions caused by removal of a decapacitation factor. To cause these two phenomena, calcium and glucose are conceivably required.
A ketone body induces an active motion state of sperm and plays an important role in maintaining sperm's motility (Patent Literature 1). Further, many reports have focused on effect of e.g., an antioxidant on activation of sperm (Patent Literature 2, etc.).
Since an excessive amount of reactive oxygen inhibits action of sperm, an antioxidant has been drawn attention as an agent for activating sperm. For example, at present, a reactive oxygen removing substance such as glutathione, SOD and taurine is added; EDTA is added for the purpose of suppressing reactive oxygen and removing metal ions; and an antioxidant such as coenzyme Q10 and a catechin is used.
However, mechanism of action and clinical effect of these sperm activating agents have not yet been elucidated and an effective method for improving fertility has not yet been available in clinical sites.